As mobile phones, digital AV devices, IC cards and the like are highly functionalized, it is more demanded that a semiconductor silicon chip (hereafter referred to as “chip”) be highly integrated in a package by making a mounted chip smaller and thinner. For instance, there is a demand for thinning of an integrated circuit obtained by packaging a plurality of chips, such as CSP (chip size package) and MCP (multi-chip package). In order to fulfill high integration of a chip in a package, it is necessary to thin a chip down to a range of 25 μm to 150 μm.
However, a semiconductor wafer (hereafter referred to as “wafer”) serving as a base of a chip becomes thin by grinding. Therefore, strength of the wafer decreases. This is likely to result in a crack or a warpage in the wafer. Furthermore, it is difficult to automatically carry the wafer whose strength decreases due to its smaller thickness. Therefore, it is necessary to manually carry the wafer and it is troublesome to handle the wafer.
For this reason, there has been developed a wafer handling system for reinforcement of a wafer, by which to bond a plate-like member called “support plate” which is composed of glass, silicon, hard plastic or the like, to a wafer to be ground, thereby preventing a crack and a warpage in the wafer. Since such a wafer handling system can reinforce a wafer, it is possible to automatically carry a semiconductor wafer having been made thinner.
In the wafer handling system, (i) a wafer and a support plate are bonded (temporarily attached) together with the use of various kinds of thermoplastic resins or adhesives, (ii) the wafer bonded to the support plate is thinned, and then (iii) the support plate is separated from the wafer prior to dicing of the wafer.
Patent Literature 1 discloses a technique by which to suitably attach the support plate to the wafer temporarily and suitably separate the support plate from the wafer. The technique disclosed in Patent Literature 1 uses a laminate which (i) is constituted by a grinding target base, an adhesive layer in contact with the grinding target base, a light-heat conversion layer containing a light absorbing agent and a pyrolytic resin, and a light-transmitting supporting member and (ii) is arranged such that, when the light-heat conversion layer is irradiated with radiant energy after the surface of the grinding target base which surface is opposite to the adhesive layer is ground, the light-heat conversion layer is pyrolyzed so that the ground base and the light-transmitting supporting member are separated from each other. In a case where the support plate (supporting member) is temporarily attached to the wafer (base) by utilizing such a laminate, the wafer and the support plate can be easily separated from each other by irradiating the light-heat conversion layer with light.